// 二维码
function Checknum(imgname, canvasname) {
  var nums = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '0',
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
  ]
  var verVal
  var checkNumImgName = ''
  var checkNumCanvasName = ''

  /**
   * 此方法用于生成二维码
   * @return  生成的二维码字符串
   * @param {图片id} imgname
   * @param {canvas 的id} canvasname
   */
  function initChecknum(imgname, canvasname) {
    checkNumImgName = imgname
    checkNumCanvasName = canvasname

    resetCode()
    // verVal = drawCode()
    return verVal
  }

  return initChecknum(imgname, canvasname)

  // 绘制验证码
  function drawCode(str) {
    var canvas = document.getElementById(checkNumCanvasName) // 获取HTML端画布
    var context = canvas.getContext('2d') // 获取画布2D上下文
    context.fillStyle = '#f2feea' // 画布填充色
    context.fillRect(0, 0, canvas.width, canvas.height) // 清空画布
    context.fillStyle = '#4aa32a' // 设置字体颜色
    context.font = '90px Arial' // 设置字体
    var rand = []
    var x = []
    var y = []
    for (var i = 0; i < 4; i++) {
      rand.push(rand[i])
      rand[i] = nums[Math.floor(Math.random() * nums.length)]
      x[i] = i * 60 + 30
      y[i] = Math.random() * 30 + 90
      context.fillText(rand[i], x[i], y[i])
    }
    str = rand.join('').toUpperCase()
    // 画3条随机线
    for (var j = 0; j < 3; j++) {
      drawline(canvas, context)
    }

    // 画30个随机点
    for (var k = 0; k < 30; k++) {
      drawDot(canvas, context)
    }
    convertCanvasToImage(canvas)
    return str
  }

  // 随机线
  function drawline(canvas, context) {
    context.moveTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)) // 随机线的起点x坐标是画布x坐标0位置，y坐标是画布高度的随机数
    context.lineTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)) // 随机线的终点x坐标是画布宽度，y坐标是画布高度的随机数
    context.lineWidth = 0.5 // 随机线宽
    context.strokeStyle = 'rgba(50,50,50,0.3)' // 随机线描边属性
    context.stroke() // 描边，即起点描到终点
  }

  // 随机点(所谓画点其实就是画1px像素的线，方法不再赘述)
  function drawDot(canvas, context) {
    var px = Math.floor(Math.random() * canvas.width)
    var py = Math.floor(Math.random() * canvas.height)
    context.moveTo(px, py)
    context.lineTo(px + 1, py + 1)
    context.lineWidth = 0.2
    context.stroke()
  }

  // 绘制图片
  function convertCanvasToImage(canvas) {
    document.getElementById('verifyCanvas').style.display = 'none'
    var image = document.getElementById(checkNumImgName)
    image.src = canvas.toDataURL('image/png')
    return image
  }

  // 点击图片刷新
  function resetCode() {
    var verifyCanvas = document.getElementById(checkNumCanvasName)
    if (verifyCanvas && verifyCanvas.parentNode) {
      verifyCanvas.parentNode.removeChild(verifyCanvas)
    }
    // $('#verifyCanvas').remove()
    // $('#code_img').before('<canvas width='100' height='40' id='verifyCanvas'></canvas>')
    verifyCanvas = document.createElement('canvas')
    verifyCanvas.id = checkNumCanvasName
    var img = document.getElementById(checkNumImgName)
    img.parentNode.insertBefore(verifyCanvas, img)
    verVal = drawCode()
    return verVal
  }
}

export { Checknum }
